Exploration licence No. 678, Ban Ban, NT annual report on exploration for year ending 4th October, 1974

Abstract

Detailed mapping and costeaning in the area covering the main lead-zinc anomaly has revealed a shear zone consisting of a number of mostly sub-parallel, discontinuous shears. The shear zone is approximately 1500 metres long and averages 0.4% lead and 0.25% zinc. At Olive Mine the shear zone generally contains 1% to 2% lead with a rich pocket containing about 40% lead and 3.5 oz/ton silver. It is possible that, like Woodcutters Prospect near Rum Jungle, this is only the surface expression of richer mineralization at depth. it is recommmended that the prospect be drilled, possibly using Comalco?s Gemco drill. It is envisaged that the holes would need to be drilled to a depth of at least 100 to 150 metres. However, due to the generally poor outcrop and subsequent lack of information about the direction and magnitude of the dip of the shears, further information would probably be required prior to drilling. Thus it is recommended that some geophysical survey or surveys be carried out at Olive Mine and other mineralized areas, especially near costean OL8. Difficulties will be encountered with any of the generally-used geophysical methods, especially the electrical methods as the weathering probably often extends to 30 metres or more and graphitic and possibly pyritic shales occur throughout the area, often adjacent to the shear zone. A number of geophysical surveys were carried out over Woodcutters, which has a similar geological environment to Ban Ban, including electromagnetic (Slingram and Turam), gravity, radiometric, self potential, and induced polarization. None of these were very successful although SP gave the best anomaly over the known mineralization. I would suggest using either SP or IP or both, although I stress that neither may give satisfactory results. A magnetometer survey would also prove useful in more accurately delineating the boundary of the amphibolite (dolerite) and would involve relatively little work as a 50 metre grid is already laid out. Prior to any further work, it would be advisable to relog, and sample if possible, the three diamond drill holes put down in the Brock's Creek area by Enterprise Exploration (Patterson, 1959), especially D.D.M. B.C.2 near Ban Ban Homestead. The core is apparently held by C.R.A.E. in Darwin and Ian Johnson has indicated his willingness to allow us to examine this core. I do not think this core has been sampled and analysed by either Enterprise Exploration or C.R.A.E.. Mention is made of dolomitic rocks in the log of D.D.H. B.C.2 and this should be specifically checked when relogging and analysed for if necessary. It should also be noted that the No. 4 and No. 5 Bore Holes drilled at the Zappopan Mine in 1914 (Jensen, 1915) intersected galena and cerussite (assaying up to 10% Pb) in a geological environment similar to that at Ban Ban, i.e. black shale, shale, siltstone, breccia, amphibolite, and amphibolite schist (sheared amphibolite?), and approximately on the same strike line as the beds at Ban Ban.